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aft Giorgi Khazaradze

Tbilisi, July10, 2014

Study of hexaferrite Ba0.6Sr1.4Zn2Fe12O22 by EPR technique

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Ferroelectric and Ferromagnetic orderings Schematic picture of Multiferroic

What is Multiferroics?

Read withGMR

Multiferroic

Write with avoltage

MF-RAM

[M. Bibes and A. Barthélémy, Nat. Mater. 7, 425 (2008)]D. Khomshii, Physics 2, 20 (2009)

P=α HM=α E

Magnetoelectric effect

Pij=eij x (si x sj) Dzyaloshinskii-Morya interaction

Cycloidal spin ordering

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Schematic crystal structures of hexaferrites. The (110) cross section views of an M-type (Ba,Sr)Fe12O19, W-type (Ba,Sr)Me2 Fe16O27, X-type (Ba,Sr)2 Me2Fe28 O46 , Y-type (Ba,Sr)2Me2

Fe12O22, Z-type (Ba,Sr)3Me2 Fe24 O41 , and U-type (Ba,Sr)4Me2Fe36O60 with the c axis vertical.

The (Fe,Me)-O-(Fe,Me) bond angles surrounded by dashed blue ellipsoids are strongly affected by the ratio of Sr to Ba.

Kimura et al., Annu. Rev. Condens.Matter Phys. 2012. 3:93–110]

Type of hexaferrites

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a) cristal sructure, b-d magnetic structure of Y-type hehaferrite.b) The proper-screw, c) the transverse-conical, d) the conical

Kimura et al., Annu. Rev. Condens.Matter Phys. 2012. 3:93–110]

a b c d

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Magnetic field dependence of electric polarization at different Temperatures and magnetic phase diagram of High-T MF hexaferrite Ba0.5Sr1.5Zn2Fe12O22 with magnetic field perpendicular to the c axis

T. Kimura et al. Phys Rev. Lett. 94,137201 (2005)

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Short description of EPR

• Zeeman splitting by magnetic field.• 9.6 GHz electromagnetic wave is

absorbed.• Linewidth of EPR is caused by the

interaction between the ions.

Ez=h𝝂=gµβH

Ez −Zeeman energy

𝝂− 𝑡ℎ𝑒 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑦 𝑜𝑓 the microwave field

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A. Maisuradze Aet al., Phys. Rev. Lett., 108, 247211 (2012).

Idea: apply electric field modulation and try to detect magnetic resonance in ME materials

H=H‘+HmSin(2π𝝂mt) H‘−𝑺𝒕𝒂𝒕𝒊𝒄 𝒂𝒑𝒑𝒍𝒊𝒆𝒅 𝒎𝒂𝒈𝒏𝒆𝒕𝒊𝒄 field

Hm−Modulation amplitude 𝝂m−Modulation frequency 𝝂m−100KHz

P(t)=PmSin(2π𝝂mt) P(t) –Detected absorbed

power

Schematic picture of the experiment and the Magnetic/Electric field directions

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Electric-field modulated FMR is selectively sensitive to Magnetoelectric coupling in Cu2OSeO3

A. Maisuradze et al., Phys. Rev. Lett., 108, 247211 (2012).

Temperature dependence of FMR signals of single-crystal Cu2OSeO3

detected using the MFM technique and the EFM technique

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Ferromagnetic resonance in Y-type hexaferrite Ba0.6Sr1.4Zn2Fe12O22

Angular dependence of the resonance field

θ

C axis

H

0 2000 4000 6000 8000

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

T=293K

Ba0.6

Sr1.4

Zn2Fe

12O

22

FM

R S

igna

l, a.

u.

Magnetic Field, G0 15 30 45 60 75

1500

3000

4500

6000

7500

Res

onan

ce fi

eld,

G

Angle , Degree

B C

Ba0.6

Sr1.4

Zn2Fe

12O

22

T=293K

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Ferromagnetic resonance in Y-type hexaferrite Ba0.6Sr1.4Zn2Fe12O22 with Electric field modulation

2000 4000 6000 8000

-300

-200

-100

0

100

200

T=293K

Ba0.6

Sr1.4

Zn2Fe

12O

22

FM

R S

igna

l, a.

u.

Magnetic Field, G

500 1000 1500 2000 2500

0.05

0.10

0.15

0.20

0.25

Ba0.6

Sr1.4

Zn2Fe

12O

22

Am

plitu

de, a

.u

Electric field, V

Amplitude of firs FMR Line Amplitude of firs FMR Line

T=273K

FMR signal at Electric fieldThe amplitude of FMR signal as function Electric field

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Magnetic and Electric Field Modulated FMR (EFMR) in Ba0.6Sr1.4Zn2Fe12O22

0 2000 4000 6000 8000

-0.4

-0.2

0.0

0.2

0.4

Ba0.6

Sr1.4

Zn2Fe

12O

22

=600

T=293K

FM

R S

igna

l, a.

u.

Magnetic Field, G

Magnetic Electric

0 2000 4000 6000 8000

-0.4

-0.2

0.0

0.2

0.4

0.6

=900

T=293K

Ba0.6

Sr1.4

Zn2Fe

12O

22

FM

R S

ignal,

a.u

.

Magnetic Field, G

30 45 60 75 90 1051E-8

1E-7

1E-6

T=293K

Coupling at second FMR line Coupling at first FMR line

T=293K

Ba0.6

Sr1.4

Zn2Fe

12O

22M

agni

toel

ectr

ic c

oupl

ing,

Angle , Degree

Angular dependence of the Magnetoelectric (ME) coupling

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Summary and Conclusions• Ferromagnetic resonance (FMR) in Y-type hexaferrite

single crystal Ba0.6Sr1.4Zn2Fe12O22 was observed.

• Using electric field modulation FMR (EFMR) technique magnetoelectric coupling was observed in this compound.

• Magnetoelectric coupling was estimated, however it is week at room temperature.

• Magnetoelectric coupling was determined quantitatively as a function of temperature and magnetic field orientation.

• The next step would be to study this compound at lower temperatures and appropriate magnetic field range where electric polarization was observed by using Soft X-ray Scattering method.

Outlook

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Thanks for your Attention!